Rail workers today voted for the first national strike in 20 years just hours after controversial laws to curb walk-outs were confirmed by the new Business Secretary.

Members of the Rail, Maritime and Transport union backed the industrial action in a row over pay, by 4-1 on a turnout of 60 per cent. “This is a massive mandate for action and shows the anger of safety-critical staff across the rail network at attacks on their standards of living and their job security,” said RMT general secretary Mick Cash.

The union pointed out that the ballot result comfortably outstripped proposed new rules on strikes proposed by the new Tory government.

Earlier this morning Business Secretary Sajid Javid said public sector strikes would be banned unless backed by at least 40 per cent of staff eligible to vote. He spoke out ahead of the result of the ballot of 16,000 RMT members seeking pay rises, including signalling and operations staff and track maintenance workers.

The Transport Salaried Staffs Association was also balloting its members, with the result due over the next week. The date of the strike, which could stop millions of commuters getting to work, has yet to be announced.

David Cameron presides over his first Cabinet meeting of the new Government

The clash with the unions came as the Prime Minister carried on with the first Conservative-only reshuffle since John Major’s era, putting rising talents into the middle and junior ranks. Among the eye-catching promotions:

Caroline Dinenage becomes junior minister at Justice as well as Minister for Equalities at the DfE.

James Wharton, who piloted a Bill for an EU referendum, becomes a minister for the flagship Northern Powerhouse agenda. David Cameron was this afternoon visiting the North-East to underline his backing for regional jobs growth.

Former diplomat and explorer Rory Stewart is junior minister at Defra, while Ben Gummer, son of former Cabinet minister John, now Lord Deben, is junior health minister.

Speaking on BBC radio, Mr Javid said reports of a “war” between the Government and the BBC were “over-excited”. But he confirmed legislation in the first Conservative Queen’s Speech since 1996 would rule strike ballots invalid unless at least half of the workforce took part.

In another measure, the Conservative Government will repeal a ban on the use of agency staff to fill in for striking employees. “That’s something we’ll give more detail on in the Queen’s Speech but it will be a priority,” said Mr Javid, one of several key promotions in Mr Cameron’s reshuffle. He added: “I think it’s also something that needs to be done. We need to update our strike laws and we’ve never hidden away from the changes we want to make.”

The minister also did not deny his deregulation agenda could include a bid to revive the “fire at will” proposals for employment reform that were blocked by his Liberal Democrat predecessor Vince Cable. A second strike ballot was due to be announced this afternoon over RMT calls for industrial action on the Docklands Light Railway. It alleges harassment of staff.

Other junior reshuffle moves today made Justin Tomlinson Minister for Disabled People, Damian Hinds Treasury Minister, John Penrose junior minister at the Cabinet Office, Mark Lancaster Veterans Minister, Marcus Jones Communities and Local Government and Ben Wallace Northern Ireland. Tracey Crouch MP, a football coach and FA referee, is the new Minister for Sport.

Mr Cameron was telling his first Cabinet meeting since the election that the Conservatives would be the “real party for working people”.

He will announce legislation that will be introduced within weeks to reform welfare, offer more apprenticeships, create jobs and assist with childcare costs.

He was due to say: “Every decision we take, every policy we pursue, every programme we initiate, never forget: we’re here to give everyone in our country the chance to make the most of their life.”